The embodiment relates to an antenna.
In recent, as an antenna has been diminished, the radiation efficiency and gain of the antenna are deteriorated, and the bandwidth of the antenna becomes narrower. In spite of the deterioration of the electrical performance, as the demand for the miniaturization, multifunction and wide bandwidth of the mobile terminal have been increased, the miniaturization, multiband and high performance for the antenna have been continuously required.
In the initial stage, a ¼ wavelength monopole antenna is used as an embedded antenna, or a helical type external antenna is mainly used for the mobile terminal. However, these antennas cause inconvenience to a user in carrying the mobile terminal, and radiation efficiency and robustness of the antennas are deteriorated.
In order to solve these problems, studies for the embedded antennas have been actively performed. Specifically, the study for an inverted-F antenna has been performed very actively. Since the inverted-F antenna has the flat plate structure can be fabricated in a simple way, the inverted-F antenna can be easily applied as the embedded antenna, so the inverted-F antenna has been extensively used as an embedded antenna for a mobile terminal.
FIG. 1 is a perspective view showing a general inverted-F antenna of the related art.
Referring to FIG. 1, in order to satisfy the multiband, the general inverted-F antenna includes a radiator 10 having a low-frequency pattern portion 11 and a high-frequency pattern portion 12 and formed in a conductive pattern of a predetermined shape, and a frame having a predetermined shape with a top surface onto which the radiator 10 is assembled and fixedly supported.
A structure of the inverted-F antenna has been variously modified in use.
However, since an embedded antenna such as an inverted-F antenna is installed in a small space, the antenna size is limited, so that the input impedance has a great capacitive reactance with a low resistance. When the reactance is removed by using a matching circuit, the inverted-F antenna has narrowband characteristics rather than wideband characteristics.
Further, because of low-resistance characteristics, the radiation efficiency is decreased, so it is difficult to effectively satisfy the wideband and multiband characteristics required in recent.